Vegetable oils are typically oils that have been pressed or extracted, such as from a vegetable source. Many vegetable oils contain some form of phosphatides (e.g., hydratable or non-hydratable), commonly known as gums. For instance, soybean oil contains about 1-3%, corn oil 0.6-0.9%, sunflower oil 0.5-0.9%, and canola oil (crude) 1-3% of gums.
Gums can be partially or totally removed from vegetable oils through several different known degumming processes. The most commonly used processes in the industry are water degumming, acid degumming, caustic refining and enzymatic degumming, for example, as disclosed in U.S. Pat. Nos. 4,049,686; 5,239,096; 5,264,367; 5,286,886; 6,001,640; 6,033,706; 7,494,676 and 7,544,820, and U.S. Pat. Pub. Nos. 2007/0134777; 2008/0182322 and 2012/0258017.
Other degumming processes include the use of high shear mixers, for example, the processes disclosed in U.S. Pat. Nos. 4,240,972; 4,698,185; 6,172,248 and 8,491,856. It has been proposed to refine vegetable oil using cavitation, such as that disclosed in U.S. Pat. Nos. 8,911,808; 8,945,644 and 9,481,853.
Many conventional processes employ chemical degumming for removal of gums from oil. Recently, more attention has been focused on enzymatic degumming because enzymatic degumming can provide a better oil yield than water, acid, or caustic degumming, and thereby contribute improved economic results. The principle of enzymatic degumming is to convert non-hydratable phospholipids into hydratable phospholipids, which can then be removed by separation processes. The enzymes are in the water phase and interact with the phospholipids at the interface between oil and water. Enzymes exhibiting activity with phospholipids are commonly called phospholipases. The types of phospholipase are based on the position on the phospholipid molecule at which the enzyme reacts, and are known as PLA1, PLA2, PLC, PLB and PLD.
The typical enzymatic degumming process for vegetable oils includes four main steps. First, the pH of the vegetable oil is adjusted with an aqueous acid and caustic to a value of 3 to 7 and the phospholipids are brought from the oil to an oil/water interface, by obtaining a vegetable oil-water emulsion. The vegetable oil-water emulsion and an aqueous enzyme solution is then dispersed together to enzymatically degum the vegetable oil. The mixture is stirred in an enzymatic reactor to facilitate enzymatic degumming of the vegetable oil at a temperature of 20° to 90° C. to obtain a liquid which contains degummed vegetable oil and a watery sludge. The liquid is further processed to separate the degummed oil from the watery slude.
While enzymatic degumming offers significant advantages to oil processors, it also poses certain disadvantages. One disadvantage is that the reaction of the enzyme with the phospholipids can be slow and time consuming. In particular, the reaction of the enzymes with phospholipids can take 2 to 6 hours, depending on reaction variables such as pH, temperature, relative concentrations, and mixing conditions. PLA, for instance, generally requires a reaction time of at least about 4 hours, while PLC requires a reaction time of about 2 hours. The processes can require an enzymatic reactor tank for housing the mixture for period of 2-6 hours, depending on the quality of the incoming oil. Such prolonged reaction times can have a significant negative impact on the overall efficiency and economic value of enzymatic degumming processes. While enzymatic treatment processes show good potential, the present invention provides solutions for improving oil degumming processes that overcome known disadvantages.